Evaluation of articulated tower-ocean wave energy converter (AT-OWEC) – Part I: The dynamic behavior under wave excitation

In this paper, a new type of ocean wave energy converter designated as the Articulated Tower-Ocean Wave Energy Converter (AT-OWEC) is introduced, especially for operation in Indonesian waters. The working principle is converting the rotational pitching motion of AT as the main structure when induced by wave excitation into translational motion of an arm to propel a double action piston pump (DAPP) which drive the water jet to move a turbine and hence generate electricity. At this stage the work is concentrated in the evaluation of the AT dynamic behavior under regular wave excitation. The formulation of the AT rotational pitch motion in 1-DOF is described, and is followed by the modelling utilizing analytical and numerical models. A case study is conducted on 3 variations of AT size to be operated in three different water depths d, namely 10.0 m, 15.0 m and 20.0 m. The variants are made of steel sized, Variant #1 Dh = 2.0 m, H_h = 3.5 m, t = 10.0 mm, Variant #2 D_h = 3.0 m, H_h = 4.5 m, t = 25.0 mm, and Variant #3 Dh = 4.0 m, Hh = 5.5 m, t = 30.0 mm. The results of the analysis show the largest RAO pitch motion occur in the case of Variant #1 when operated in the water depth d = 10.0 m reaching 49.24 deg/m, while the lowest one occurs in the case of this variant when operated in d = 20.0 m with the intensity of only 16.06 deg/m. Nonetheless, AT of Variant #3 is found to be more potential to harvest the greater wave energy in conjunction with the peculiar characteristic of the Indonesia sea wave frequency range.